(NewsNation) — Weeks after a nationwide string of attacks on power stations — which knocked out power to tens of thousands of Americans — the Federal Bureau of Investigation has cracked at least one of the cases.

On Wednesday, 32-year-old Matthew Greenwood and 40-year-old Jeremy Crahan of Washington state are in custody, facing federal charges of conspiracy to damage an energy facility.

“It’s a very significant federal charge to damage energy facilities,” said Nick Brown, United States Attorney for the Western District of Washington.

In charging documents, prosecutors say the men attacked four substations near Tacoma on Christmas Day, which “resulted in approximately $3 million dollars’ worth of damage” and cut power to nearly 14,000 homes for hours.

The attacks demonstrate the staggering vulnerability of energy facilities to disorganized, low-tech vandalism and the concerns of law enforcement about the chaos that can follow.

“I think it’s important to recognize that these can be particularly vulnerable targets,” Brown said. “Because often there’s not much security or infrastructure around them. Often they’re in more remote areas.”

The key to identifying the suspects in Washington state was cell phone tower information that placed both Greenwood and Crahan at each of the four substations at the time of the attacks.

Surveillance images also helped the FBI match the clothing and one of the suspect’s pickup trucks to the alleged attackers.

The complaint stated: “Greenwood stated that Greenwood and Crahan have been planning to disrupt power to commit a burglary.”

Authorities said one suspect told police they did it so they could break into a business and steal money from a cash register.

Greenwood is additionally charged with possession of unregistered firearms for illegal weapons the FBI found in a search of his property.

Damaging an energy facility under federal law in excess of $100,000 may carry a sentence of not more than 20 years in prison, a fine or both.

An attorney for Crahan tells NewsNation that if his client is indicted, he expects him to plead not guilty.

There are still unsolved cases of power station attacks in Oregon, Washington and North Carolina.